Porcelain enamel finish



Patented Apr. 12-, 1949 PORCELAIN ENAMEL FINISH Eugene E. Bryant,Bedford, Ohio, assignor to Ferro Enamel Corporation, Cleveland, Ohio, a

corporation of Ohio No Drawing.

Application May 27, 1944,

Serial No. 537,722

. 2 Claims. 1

This invention relates as indicated to porcelain enamel finishes andmore particularly to a method of producing a useful and decorativeeffeet on all or preferably only a portion of the surface of the enamelby an expedient which prevents the formation, during the normal firingoperation, of the usual smooth glassy surface of the enamel. There aremany cases where the protective or decorative properties of conventionalporcelain enamel are desirably utilized but which, for certain reasons,require an ultimate finish which is not the smooth glassy surface ofporcelain enamel in its normal fired state.

When the work-piece is a structural element such as a shingle or roofingpiece, architectural considerations require that for best results thesurface be a very fine matte finish. In other cases, such as in thefloors of bath tubs, shower stalls, and the like, the glassy smoothsurface of porcelain enamel is objectionable because of the slippinghazard. Here again, there is a requirement that the enamel finish have afine matte surface and one which may be readily cleaned.

It is a principal object of my invention to provide a porcelain enamelfinish and an improved method for producing the same characterized in animproved matte surface texture and one which may be secured at anunusually low cost,

Other objects of my invention will appear as the description proceeds.

To the accomplishment of the foregoin and related ends, said inventionthen comprises the features hereinafter fully described and particularlypointed out in the claims, the following description setting forth indetail certain illustrative embodiments of the invention, these beingindicative, however, of but a few of the various ways in which theprinciple of the invention may be employed.

Broadly stated, this invention comprises the discovery that an improvedmatte finish for porcelain enamels may be provided by first applying tothe work a continuous layer of porcelain enamel forming material of suchcomposition that when fired under normal conditions it will yield asmooth glassy surface, and then depositing on such layer, prior tofiring, a relatively thin coating of a very finely divided materialwhich is substantially infusible in the firing range of the enamelforming material. This composite coating is then fired in the normalfiring range of the porcelain enamel forming material. The applied thinsecond coat is preferably of such fineness that substantially all willpass through a 200 mesh sieve and preferably through a 325 mesh sieve.

The materials used in carrying out my invention may be divided into twogeneral classes, i. e. the porcelain enamel forming materials and thematte surface forming materials.

The porcelain enamel forming materials may be any conventional porcelainenamel of which there are many available on the market today. Anyporcelain enamel, whether white or with added color, or whether it beadapted for direct application to the Work, or as a cover coat over aground coat, may be employed. While thus any conventional porcelainenamel may be used, generally best results will be secured by the use ofan acid resistant enamel since this type has greater durability undermost conditions. It is believed unnecessary to give the formula for anyof the enamels which may be used since there are a number ofpublications and prior art patents from which a wide variety ofcompositions may be secured.

The porcelain enamel forming materials are generally applied to the Workin a conventional fashion as by first forming a slip and then applyingthesame to the previously cleaned workpiece, either by brushing,spraying, or dipping. The thickness of the porcelain enamel formingmaterial coat will be determined by the usual considerations such as thenature of the enamel itself and the nature of the use for which thework-piece is designed.

The matte surface forming materials which may be applied to the coatedwork-piece prepared as just described, either before or after drying,will now be briefly explained.

The matte surface forming materials useful in carrying out my inventionshould be substantially infusible in the firing range of the enamelforming materials, That is, my invention does not rely on an interfusionof the porcelain enamel and the matte forming materials, but rather uponthe matte forming materials because of their presence exerting aphysical action on the surface of the enamel during the firing operationand preventing the same from becoming glassy smooth.

Materials useful for this purpose are most of the well-known enamelersclays. These are selected for use because of considerations such as lowcost, the fact that they are substantially infusible in the firing rangeof the enamel, and because they are in their natural state in extremelyfinely sub-divided form requiring no grinding as such for the purpose ofreducing the particle size. While clay is thus an admirable material forthis purpose, it is, nevertheless, possible to use any other mineralsubstance which is substantially infusible in the temperature range atwhich the enamel is'fired and which may be conveniently reduced as bygrinding in a ball mill to a particle size such that substantially allwill pass through a 200 mesh sieve and preferably to a fineness suchthat all will pass through a- 325 mesh sieve. At this point, I mightexplain that for best results I prefer the very finest particle sizematerials obtainable.

Any finely divided mineral material or synthetic refractory material,which is substantially infusible in the firing range of the enamel, maybe employed. Examples of such materials are kaolin, calcined kaolin,feldspar, silica, aluminum silicate, and zircon sand, i. e. zirconiumsilicate.

These matte surface forming materials may be applied either by dustingor spraying. When these materials are applied to the coat of enamelforming materials before the latter is dried, then the matte surfaceforming materials may be in a dry state, whereas, if the enamel formingcoat has first been dried or even when it is in. the undried state, thematte surface forming materials may be applied by means of a sprayhaving, first been formed into a slurry by the addition of a suificientamount of water.

The weight of application of the matte surface forming materials shouldbe as thin as possible. The theoretically perfect weight of applicationis a coating of one particle thickness. It will generally be found thatbest results will be secured if thefiring operation and weight ofapplication are so controlled that at the conclusion of the firing onlythe first layer of particles of matte surface forming material willadhere to the fired enamel. The excess may either be removed as bywashing or brushing or, if there is no objection, the article may beplaced into use with the loosely adherent excess of matte surfaceforming material thereon, since, if the article is exposed to theweather or to the flow of water thereover, it will be found that theexcess is soon washed off.

In the preferred embodiment of my invention, the matte surface formingmaterial is applied not asa continuous layer but instead as a stipplecoat. A stipple coat may be conveniently applied by the use of aconventional spray gun and by adjusting the nozzle so that instead ofejecting a stream of finely divided particles, the gun will projectlarge globules which may be splattered on the work-piece to provide thestipple deposit.

I. have discovered that a very desirable surface for many purposes maybe provided by the application of a stipple coat of the matte surfaceforming materials such that only a minor proportion of the entiresurface of the article has the matte finish, whereas, the remainder ofthe article surface is the conventional glassy smooth surface of thefired porcelain enamel. A stipple coatv thus applied breaks upreflectance areas to such an extent that even when viewed in reflectedlight the entire surface of the article has the appearance of a mattefinish, even though only a minor proportion of the entire surfaceactually has the matte finish. This is also true when providing non-slipsurfaces for the floors of shower stalls and bath tubs. It has beenfound that a surface on which the matte finish is provided by means of astipple coat, comprising only a minor proportion of the entire surface,provides as much anti-skid or anti-slip protection as though the entiresurface were a. matte finish.

The area between the stippled areas being glassy smooth may be cleanedas readily as conventional porcelain enamel, thus providing a surfacewhich combines all of the ease of cleaning of a glassy'smooth surfacewith the full non-slip protection of a full matte surface. By aselection of proper color combinations, for the body of 4 the enamelsurface and the stippled areas where the matte finish is provided, onemay select a combination which is entirely pleasing to the eye eventhough the segregated matte surfaces may change their color during use.

In addition to the use of my improved finish as a coating for non-slipsurfaces such as in bath tubs and the like, I have found a wide field ofuse for such finish in the architectural field and particularly as ameans for providing a protective and decorative coating on corrugatedsheet iron roofing. In such cases, as well as fiat panels applied to thewalls, either interior or exterior, of a building, the relatively smallproportion of the matte finish areas when applied as a stipple coat areeffective to break up the large reflectance areas giving the appearanceof a full matte finish while at the same time preserving, however, allof the advantages of a smoothly fired finish such as ease of cleaningand the color effects which may be secured with smooth surfaces andwhich are not possible with surfaces which have a matte finishthroughout their extent.

Other modes of applying the principle of the invention may be employed,change being made as regards the details described, provided thefeatures stated in any of the following claims or the equivalent of suchbe employed.

I therefore particularly point out and distinctly claim as my invention:

1. A porcelain enamelled article comprising a workpiece with an adherentcoating of porcelain enamel, the surface of which is glassy smooth butwhich has a matte finish stippling of clay, the total area of which is aminor proportion of the whole surface.

2. A porcelain enamelled article comprising a workpiece with an adherentcoating of porcelain enamel; the surface of which is glassy smooth butwhich has a matte finish stippling of finely divided mineral materialwhich is substantially infusible in the firing range of said enamel andhas a fineness such that substantially all will pass through a 200 meshsieve, the total area of which is a minor proportion of the wholesurface.

EUGENE E. BRYANT;

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 329,165 Hines Oct. 27, 1885596,317 Bentz Dec. 28, 1897 806,153 Kohler Dec. 5, 1905 842,993 ArcherFeb. 5, 1907 1,438,154 Zulauf Dec. 5, 1922 1,497,397 Zulauf June 10,1924 1,784,392 Rowland -1 Dec. 9, 1930 2,020,477 Scott Nov. 12, 19352,197,803 Jewett Apr. 23, 1940 2,292,369 Gordon Aug. 11, 1942 2,327,972Stettinius et al Aug. 24, 1943 2,337,691 Stettinius et al. Dec. 28, 1943FOREIGN PATENTS Number Country Date 37,958 Germany 1886 150,825 Austria1937

